Cooee is primarily a call for attention when separated by distance. After wandering off the trail, he shouted 'cooee' to alert the others.
Pro Tip 2/3
Outdoor Use
Use 'cooee' outdoors; it carries well over long distances in natural settings. From the mountain top, her cooee rang clear into the valley.
Pro Tip 3/3
Not for Indoor
Avoid using 'cooee' in indoor or formal settings; it's intended for open spaces. Instead of shouting 'cooee' in the library, I looked around for my friend.